TY - JOUR
T1 - Flames structure measurement of single, isolated aluminum particles burning in air
AU - Bucher, P.
AU - Yetter, R. A.
AU - Dryer, F. L.
AU - Parr, T. P.
AU - Hanson-Parr, D. M.
AU - Viceni, E. P.
N1 - Funding Information:
This work was supported by the Office of Naval Research under contracts N00014-93-1-0732 and N00014-95-1-1339, subgrant 96-184. PLIF measurements were conducted collaboratively at the Naval Air Warfare Center, China Lake, CA. EPMA analysis was performed at the PMI, by using MRSC Shared Facilities.
PY - 1996
Y1 - 1996
N2 - Spatially resolved measurements of the flame structure about single, isolated aluminum particles burning in air were made using planar laser-induced fluorescence (PLIF) and electron probe microanalysis (EPMA). Spherical aluminum particles of 210 μm diameter were generated continuously by mechanical chopping of wire strands and laser heating, which also ignited the particles. After ignition, combustion was found to occur in two stages consisting of an initial steady burning phase, characterized by a spherical flame positioned off the surface, and a second violent, unsteady burning phase, during which gaseous ejections occurred from the particle surface. PLIF was used to measure the radial profiles of gaseous AlO and AlO vibrational temperature during the steady burning stage of particle free fall. The radial distribution of condensed-phase Al2O3 was measured by impaction and rapid quenching of individual particles and their associated oxide clouds on silicon plates. Analysis of the impacted cloud distribution was performed off-line with EPMA and Abel transform techniques. Results indicated a flame structure of finite thickness, wherein AlO is a gas-phase intermediate. Relative peak concentrations of AlO and Al2O3 were measured at r/rs=2.8 and r/rs=3.5, respectively. The temperature rose from ∼2350 K at the particle surface to a nearly constant value of ∼3800 K between 5s<6. The surface temperature agrees well with previously reported ignition temperatures, while the plateau temperature is ∼300 K higher than the theoretically predicted adiabatic flame temperature for a stoichiometric Al-air mixture. The species and temperature measurements support previously proposed models where gasification can occur by both vaporization and heterogeneous surface reactions. Transport of Al outward and reaction with inward-diffusing molecular oxygen yields AlO. Subsequent heterogeneous reactions involving AlO yield condensed-phase Al2O3 at even greater radii.
AB - Spatially resolved measurements of the flame structure about single, isolated aluminum particles burning in air were made using planar laser-induced fluorescence (PLIF) and electron probe microanalysis (EPMA). Spherical aluminum particles of 210 μm diameter were generated continuously by mechanical chopping of wire strands and laser heating, which also ignited the particles. After ignition, combustion was found to occur in two stages consisting of an initial steady burning phase, characterized by a spherical flame positioned off the surface, and a second violent, unsteady burning phase, during which gaseous ejections occurred from the particle surface. PLIF was used to measure the radial profiles of gaseous AlO and AlO vibrational temperature during the steady burning stage of particle free fall. The radial distribution of condensed-phase Al2O3 was measured by impaction and rapid quenching of individual particles and their associated oxide clouds on silicon plates. Analysis of the impacted cloud distribution was performed off-line with EPMA and Abel transform techniques. Results indicated a flame structure of finite thickness, wherein AlO is a gas-phase intermediate. Relative peak concentrations of AlO and Al2O3 were measured at r/rs=2.8 and r/rs=3.5, respectively. The temperature rose from ∼2350 K at the particle surface to a nearly constant value of ∼3800 K between 5s<6. The surface temperature agrees well with previously reported ignition temperatures, while the plateau temperature is ∼300 K higher than the theoretically predicted adiabatic flame temperature for a stoichiometric Al-air mixture. The species and temperature measurements support previously proposed models where gasification can occur by both vaporization and heterogeneous surface reactions. Transport of Al outward and reaction with inward-diffusing molecular oxygen yields AlO. Subsequent heterogeneous reactions involving AlO yield condensed-phase Al2O3 at even greater radii.
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U2 - 10.1016/S0082-0784(96)80012-9
DO - 10.1016/S0082-0784(96)80012-9
M3 - Article
AN - SCOPUS:0030365147
SN - 0082-0784
VL - 26
SP - 1899
EP - 1908
JO - Symposium (International) on Combustion
JF - Symposium (International) on Combustion
IS - 2
ER -